the thunder became violent from the zenith to S.W. by W.; then to E. by S. S., and then S.E. The wind now alternated with the rain; the thunder from N.W. to S; then heavy rain fell, with thunder to E. zenith S., and terminated in S.W. The sky began to get clear; the thunder continued in severity, with vivid flashes of lightning in various directions, and after a time all the phenomena ceased, and a most pleasant sensation was felt.

There are at this period of the year, especially at the closing of the rains or harvest, repeated recurrence of forked or penetrating and vivid flashes of sheet lightning, which in many cases occasions a peculiar sensation of a delightful and agreeable character on the exposed sentient surface. Mr Hutchinson describes it as " a dash of increased heat simultaneous with a vivid flash of lightning;" and the late Dr Baikie, as " a feeling of warmth in the face." This feeling I believe to be caused by an increased development of ozone by each flash, which, being a powerful and energetic oxidising substance, oxidises the oxidisable from transpiration emanating the surface of body. After the After effects tornado, the most pleasing sensation is felt; the air is refreshingly cold, clear, and exhilarating, containing a large quantity of oxygen, and the constitution much invigorated; for in the second tornadal observations above described, the thermometer fell from 86° to 78°, the hygrometer was 3°, dew-point 74°, saturation of the atmosphere 8814, and tension of aqueous vapour 0.957. There was an increase of 2° in the ozonometer.

of tornado.

In the Gambia region, towards the approach of the rainy season, the wind, which had been most constantly blowing from the monsoon points N., N.E., and E., now blows all the day with violence from S.W., W., and N.W., which greatly cools the atmosphere, although in some days the thermometer goes up as high as 106°. The temperature before sunrise is very chilly, and individuals are very much subject to colds and coughs. The rains here are ushered in by one or two dirt Dirt gales gales. Thus in 1866, the rainy season at M'Carthy's Island commenced literally on the 22d June. A few days previously

there was a severe dry gale from the direction between southeast and north-east, blowing with tremendous velocity everything before it. Its approach was indicated by a deep grumbling noise a mile off, and the moving column of air appeared as a dense black fog, but was composed of dirt; it removed all the light surface earth, and wafted it along with great velocity, and unless individuals were under shelter, it was impossible to breathe without taking into the lungs a large quantity of dust. It continued with varied velocity for half an hour, and then gradually subsided. On the 21st the mid-day sun was very oppressive; towards evening a strong south-west wind blew, the atmosphere clear, the moon bright and the heavens starry; at 3 A.M. of the 22d the rains were ushered in with a severe north-east wind blowing into a tornado.

On the Gold Coast and the Bights the rains commence earlier, but do not continue until September. They terminate about the beginning of June, occasioning the former rains. The latter rains commence about the beginning of July, and terminate at the end of August. But in Liberia, Sierra Leone, the Gambia, and Senegal, when the rains once commence, they gradually increase until towards the end.

of quantity

in 1829, 1858,

From the Rio Pongas to Liberia the rains are more plentiful Calculation than at any part of the coast; but the quantity varies a great of rain at deal every year. The maximum quantity which fell at Free- Sierra Leone town, Sierra Leone, according to the observation which was and 1860. taken at the military hospital in August 1860, in the twentyfour hours, was 2.61 inches, which was on the 28th of the month; in September it was 4.27 inches on the 1st; and in October, 465 on the 6th. The minimum was in August, 04 on the 10th; in September, 05 on the 23d; October, 01 on the 28th. The total quantity of rain during the whole of August was 26.86 inches; in September it was 25.35 inches; and in October, 13.80 inches. In April of the same year, the total quantity which fell was 3·56 inches; in May it was 10.24 inches; and in June it was 15.23 inches. The observations taken from the 1st to Friday the 28th.

If we refer to the tables published by Boyle, as the observations taken in the same hospital in the months of June, July, and August 1829, it will be found that the quantity of rain which fell must have been enormous, and was quite sufficient to inundate the whole of the country, mountainous though it is, and goes far to prove that there are sensible differences between the meteoric phenomena of the last thirty years and the present time.

The maximum quantity of rain in the twenty-four hours in June 1829, was 4:40 inches on the 11th; in July it was 14:15 inches on the 10th; and in August 16.00 inches on the 23d. The minimum quantity in June was 1.10 inches on the 8th; in July it was 100 inches on the 16th; and in August 1.00 on the 29th. The total quantity of rain during the whole of June was 6455 inches; during July it was up to 125.55 inches, and in August it fell to 123.80 inches.

In 1858 the total quantity of rain which fell in the three months, viz., May, June, and July, as observed in the gauge kept at Fourah Bay, Freetown, was as follow:-May, 8.95 inches; June, 12-27 inches; July, only 23.50 inches.

TABULAR SUMMARY FOR 1829, 1858, 1860.

From the above table it will be seen, that the total quantity of rain which fell in the three months of June, July, and August in 1829, was 303.90 inches; the total in May, June, and July

in 1858, was 34-72; whilst the total of the six months in 1860, viz., April, May, June, August, September, and October, was 95.04. The difference between the quantity of rain which fell in May 1858, and the same month in 1860, was 1.34 inches in favour of the latter year; whilst the difference between June 1829 and June 1858, and between the same months in 1829 and 1860, are all in favour of 1829-viz., in the first case it was 52.28 inches, and in the second 49.32. In 1860 of the same month there was more rain than in 1858 of the same month by 2.96 inches. July 1829 had more rain than July 1858 by 102.05 inches, and August 1829 more than August 1860 by 96.94 inches. It is evident, therefore, that if the table of Boyle be correct, of which I have not the least doubt, the quantity of rain in 1829 must have been excessive. The quantity in June alone is nearly twice the quantity in May, June, and July of 1858, being 64.55 and 3472 respectively; and the quantity in August alone of 1829 exceeds the quantity of the six months in 1860, viz., April, May, June, August, September, and October, by 28-76. The sum total of the rain which fell in the three months, June, July, and August of 1829, exceeds the sum total of the quantity which fell in the three months, May, June, July of 1858, and the six months, April, May, June, August, September, October of 1860, by 174-24 inches, or more than double the quantity by 44:48 inches.

What, most of my readers will ask, is an inch of rain? And what equivalent in avoirdupois weight must be understood by these figures, 303.90 inches, 3472 inches, 95.04 inches?

An inch deep of rain in one acre of land yields 22,622-5 gallons of water; but 277-274 cubic inches is equal to one gallon, therefore, an inch deep of rain in one acre of land is equal to 6,372,640 cubic inches of water, since an acre, according to the English measurement, consists of 6,272,640 cubic inches.

Rain water must be considered as the purest of natural waters, especially when collected after a long continuance of

rainy weather, and even then it will be found to contain an appreciable quantity of atmospheric air, together with some of the gases floating in it, to the extent of about 2 cubic inches of air in 100 of water. Distilled water, therefore, is the best material for experiment, a gallon of which weighs 10 lbs. ; and one inch deep of rain being equal to 22,622.5 gallons of water, consequently the rain-fall on an acre of land is equal to 226,225 lbs. avoirdupois; but 2240 lbs. is equal to one ton, therefore an inch deep of rain weighs nearly 101 tons, or more correctly, 100.993 inches.

The quantity of rain, therefore, which fell in an acre of land at Freetown, Sierra Leone, in the months of June, July, and August of 1829, was not less than sixty-six millions six hundred and fifty-nine thousand five hundred and sixty pounds avoirdupois of water, or six millions six hundred and sixtyfive thousand nine hundred and fifty-six gallons of water, or thirty thousand three hundred and ninety tons. Allowing Freetown to be about three miles square, it will contain one thousand nine hundred and two acres; and, therefore, the quantity of rain which fell in all Freetown for the three months in 1829, if measured, will not be less than twelve billions six hundred and seventy-eight millions six hundred and forty-eight thousand three hundred and twelve gallons of water, or one hundred and twenty-six billions seven hundred and eighty-six millions four hundred and eighty-three thousand one hundred and twenty pounds weight of water, or fifty-seven millions eight hundred and one thousand seven hundred and eight tons of water. What an enormous quantity for only eighty days of rain!!!

Leaving unnoticed the quantity of rain which fell in the three months of 1858, which was represented by 34.72 inches, let me consider that of the six months in 1860, which amounted to 95.04 inches; there were twenty-one million two hundred and eighty thousand nine hundred and sixty lbs. of water, or two millions one hundred and eighty thousand eight hundred and ninety-six gallons, which is equal to nine thousand five hun